A Bihar member of the legislative assembly was the 'mastermind' behind the abduction of Dr Umesh Kumar Sinha, Deputy Inspector General (CID) Pervaj Hayat said on Thursday.

Three persons were arrested from an abandoned residence of the legislator on Tuesday while the doctor was freed on Wednesday, he said. "Persons picked up during the course of investigation point to him (the MLA) as being the mastermind behind the abduction," he added.

Dr Sinha was abducted near Chuttupallughati near Ormanji, 18km from capital Patna, on April 17.

Hayat said, "One of the three arrested has confessed that he works for the MLA. The evidence against him became stronger after we learnt that Purulia police are in Patna in connection with another abduction case linked to the MLA."

The Purulia police are there to locate an abducted West Bengal-based trader Naresh Agrawala and clues so far indicate the MLA's connection, Hayat said.

Asked what led him believe that the MLA was the mastermind, Hayat said, "The most important clue we came across was the phone call which was made to the doctor's house from the MLA's house."

Explaining their modus operandi, Hayat said a gang of criminals choose their target, pick up the person and hide him in the MLA's residence with his consent till the ransom amount is received.